1. Field of the Invention
The present invention relates to a telephone device provided with a microphone and a speaker built in a body unit of the telephone device, having a speakerphone function whereby a call through a receiver of the telephone device is switched to a call through the microphone and the speaker, and more particularly to a telephone device capable of preventing the occurrence of howling caused when a dial tone produced in switching to a speakerphone function mode is received by the microphone and comes out from the speaker.
2. Description of Related Art
Conventionally, there is known a telephone device, provided with a microphone and a speaker which are built in a body unit of the device, has a speakerphone function to switch a call through a receiver to a call through the microphone and the speaker. In such the telephone device, the speakerphone function can be used by operation of a speakerphone switching key provided on a control panel of the body unit, whereby a user can make a call without lifting the receiver, namely, in a hand-free state.
In the above conventional telephone device, however, upon depression of the speakerphone switching key, a dial tone is given through the speaker and the microphone is put in an ON state. Accordingly, the dial tone is received by the microphone, and the received dial tone comes out from the speaker. At this time, it is possible to generate howling, causing a problem of change in the sound given through the speaker, thus disturbing a call.
The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide a telephone device capable of preventing the occurrence of howling caused by that a dial tone produced when a speakerphone function mode is selected is received by a microphone and is sounded from a speaker, and capable of satisfactorily making a call without any disturbance of the call in the speakerphone function mode.
Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the objects and in accordance with the purpose of the invention, as embodied and broadly described herein, a telephone device of this invention comprises a microphone and a speaker provided in a body unit, a mode selection key for selecting a speakerphone mode enabling a call through the microphone and speaker, a control panel in which a plurality of dial keys are arranged, first judgement means for judging whether the mode selection key has been operated, first control means for making the speaker ON and the microphone OFF when the first judgement means detects that the mode selection key has been operated, and second control means for maintaining the speaker in the ON state and making the microphone ON upon operation of the dial key.
According to the telephone device of the invention, when the first judgement means detects that the switching key is depressed, the first control means causes the speaker to be ON and the microphone to be OFF. Upon depression of the dial key, the second control means causes both the speaker and the microphone to be ON. Accordingly, since the microphone is made OFF when the speakerphone function mode is selected by the depression of the switching key, any dial tone is not received by the microphone, which makes it possible to surely prevent the occurrence of howling. Furthermore, both the speaker and the microphone are made ON by the second control means when a dial key is depressed, so that a normal call can be made using a speakerphone function.
According to another aspect of the present invention, there is provided a telephone device comprising a microphone and a speaker provided in a body unit, a mode selection key for selecting a speakerphone mode enabling a call through the microphone and the speaker, a control panel in which a plurality of dial keys are arranged, first judgement means for judging whether the mode selection key has been operated, first control means for making the speaker ON and the microphone OFF when the first judgement means detects that the mode selection key has been operated, second judgement means for judging whether or not a call signal from some other telephone is arriving to the telephone device after the first judgement means detects that the mode selection key has been operated, connecting means for connecting a line of the telephone device with some other telephone when the second judgement means judges that there is a call from some other telephone, and second control means for making the speaker and the microphone ON after the line-connection by the connecting means.